Buret



19, 1961 J. J. RODRIGUES, JR 3,013,435

BURET Filed April 6 1959 INVENTOR.

JOHN J ROOF/GU55, JR. BY

6M a a 20% H/S ATTORNEYS.

I United States Patent BURET John J. Rodrigues, Jr., Berkeley, Calif.,assignor to Microchemical Specialties Co., Berkeley, Calif., acorporation of California Filed Apr. 6, 1959, Ser. No. 804,312 Claims.(Cl. 73-4256) with accuracy and precision;

(4) To provide a novel and improved buret adjustable with precision andquickly resettable to a starting position;

(5) To provide a novel and improved buret capable of use in pipetting.

Additional objects of my invention will be brought out in the followingdescription of a preferred form of my invention taken in con unctionwith the accompanying drawings wherein;

FIG. 1 is a longitudinal view in section through a device involving thepresent invention;

FIG. 2 is a fragmentary view depicting important shaft relationshipsinvolved in the device of FIG. 1;

FIG. 3 is a view in section taken in the plane 33 of FIG. 1;

FIG. 4 is a view in section taken in the plane 44 of FIG. 1;

FIG. 5 is a view in section taken in the plane 5-5 of FIG. 1; and

FIG. 6 is a fragmentary view partly in section through the device ofFIG. 1.

Referring to the drawings for details of my invention in its preferredform, the device comprises a substantially cylindrical casing 1 athreaded tip 5 and provided with a passageway 7 therethrough to theinterior of the casing at which point, the

interior wall of the casing is provided with a counterbore 9.

Removably secured to the threaded tip end of this casing, is a liquidcylinder 11, the attaching end of which I is preferably flanged forsecuring by a coupling nut 13 with a sealing washer 15 between theflange of the cylinder and the proximate end of the coupling nut, and asealing ring 17 between the end of the cylinder and the threaded tip ofthe casing extension 3.

Adjacent its opposite end, the casing is provided with a closure 19while adjacent thereto are window openings 21. Within this end of thecasing is a counter 25 including a plurality of numbers wheels 27rotatably mounted on a hollow shaft 31, this counter being disposed inthe casing with the hollow shaft substantially concentric with thelongitudinal axis of the casing 1 and with the numbers wheels exposedthrough the window openings.

Passing through the hollow shaft of the counter and extendingtherebeyond at each end, is a second hollow shaft 35, that end 37 facingtoward the cylinder 11, being provided with a fine thread for engagementby a fractional nut 41.

This fractional nut is pivotally mounted on a rod 43 of small diameteranchored at its ends to fixed points within the casing and permittingthe fractional nut to slidably travel therealong in response to rotationof the second shaft 35 while the nut is held in engagement with thethreaded end 37 of this shaft.

Such threaded engagement between the fractional nut and the threadedincluding an end extension 3 having 3,013,435 Patented Dec. 19, 1961shaft is normally maintained by a pressure block 45 including asupported roller 47 urged against a flange 49 along the upper edge ofthe nut by a compression spring 51 interposed between the block and aninternal wall surface 55 of the casing.

Within the passageway 7 communicating between the cylinder 11 and theinterior of the casing, is a plunger assembly 59 preferably including asection 61 of metal within the casing, having at one end a springretainer flange 63 and at its other end being provided with a threadedrecess to threadedly secure a holding socket 65 for a glass rod or thelike section 67 of the plunger assembly. This latter section isprecision ground and snugly passes through the sealing ring 17 into thecylinder.

A compression spring 69 about the metal portion 61 of the plungerassembly and having one end disposed within the counterbore 9 and theother end bearing against the flange 63, serves to normally urge theplunger assembly into maintained engagement with the proximate end ofthe fractional nut. The overall length of the plunger assembly is suchas to cause the glass portion 67 to move a substantial distance into thecylinder 11 within the travel range of the fractional nut.

Such travel of the fractional nut is accomplished from the remote end ofthe second shaft 35. The means for accomplishing this includes a drivecap 73 affixed to the exposed end of the'second shaft by means of theset screw 75. For each complete rotation of the drive cap, thefractional nut will move a distance equal to the pitch of the thread onthe threaded end 37 of the shaft and move the plunger assembly 59forward into the cylinder a comparable minute distance.

To record such distances on the counter 25, requires a drive coupling 79between the drive cap 73 and the counter, such drive coupling includinga sleeve 81 about the extended end of the second shaft 35, terminatingat one end adjacent the first numbers wheel, in a flange 83, and at itsother end, having aflixed thereto, a pinion 85 within the drive cap.

This pinion meshes with an idler pinion 87 carried by springs or pawls91 and adapted to engage ratched teeth 93 provided within the peripheryof the first numbers wheel to form a drive clutch whereby rotation ofthe drive cap 73 in the direction of producing travel of the plungerassembly into the cylinder, will at the same time bring about rotationof the numbers wheels on the counter to accurately record such forwardmovement, when a proper ratio exists in the drive coupling 79 betweenthe drive cap and the counter. Reverse rotation of the numbers wheels,as when resetting the counter, will cause the clutch to slip and nottransmit motion back to the drive cap.

To restore the plunger assembly to its initial starting position whendesired, all that is necessary is to lift the fractional nut 41 from itsengagement with the threaded end 37 of the second shaft, whereupon boththe plunger assembly 59 and the nut 41 will be restored to their initialstarting position by the compression spring 69.

This can be effected very simply and conveniently by providing a pushpin 97 which enters the casing through the wall thereof and terminatesin a reduced threaded end for threaded engagement with the springpressed block 51 while the shoulder 99 formed by the reduced end,engages the flange 49 along the upper edge of the fractional nut. Thusby pressing in on this push pin, the fractional nut may be lifted fromits threaded engagement with the shaft, the engagement between theshoulder and the flanger permitting the nut to slide along its pivot rodmounting 43 in response to the pressure of the spring 69.

Resetting of the counter to conform with such restoration of the plungerassembly to its starting position, can be effected by providing thehollow shaft 31 with a longitudinal slot 101 adapted during reverserotation of the numbers wheels 27, to receive a pawl 103 associated witheach wheel, which upon continued reverse rotation of the shaft, willrestore its associated number wheel to starting zero position.

The shaft carries a thumb wheel 105 which is exposed through slot in thecasing to enable a user to accomplish such resetting of the counter.During such resetting operation the slip clutch constituting part of thedrive coupling between the counter and the drive cap 73 will effect adisconnection between the two.

By initially providing the counter 25 with a hollow shaft 31 toconcentrically receive the second hollow shaft 35, a rod 109 can be rundown through the second hollow shaft to effect direct contact with theplunger as sembly at its contacting end, the rod preferably beingprovided with a flange 111 to seat within a counterbore at the threadedend of the second hollow shaft to prevent withdrawal thereof, while atits exposed end, this rod will be provided with a knob 115 or the like.

The installation of this rod permits of direct actuation of the plungerassembly in drawing liquid up into the cylinder for subsequent burettingpurposes, but what is of added importance to the present device, the rodfurther permits of the use of the device in pipetting, that is in thecomplete discharge of the cylinder contents with one stroke of theplunger assembly.

In employing the device for buretting, the plunger assembly is restoredto its innermost or starting position with the counter set at zeroreading on all the numbers wheels. The maximum quantity of liquid isthen drawn into the cylinder by forcing the plunger assembly forward tothe extent provided for by the push rod, then the cylinder tip isimmersed in a liquid and the push rod withdrawn permitting the plungerassembly to restore itself to its initial position. Then by rotating thedrive knob and watching the numbers wheels on the counter, predeterminedminute amounts of the liquid may be dispensed from the cylinder asdesired.

When employing the device for pipetting purposes, a precise quantity ofliquid is to be drawn into the cylinder and then discharged all at once.Such precise quantity is measured by preliminary adjustment of theplunger assembly through manipulation of the counter. Knowing themaximum capacity of the device, the counter may be adjusted to subtractthe necessary amount to thereby reduce the capacity of the cylinder bythat same amount. When so adjusted, the device will accurately withdrawthe desired quantity of liquid into the cylinder and discharge the same,through the simple operation of manipulating the push rod.

From the foregoing description of my invention in its preferred form, itwill be apparent that the same fulfills all the objects attributedthereto, and while I have illustrated and described my invention in itspreferred form and in considerable detail, it will be apparent that thesame is subject to alteration and modification without departing fromthe underlying principles involved, and I accordingly do not desired tobe limited in my protection to such details except as may benecessitated by the appended claims.

I claim:

1, A buret assembly comprising a substantially cylindrical casing havinga liquid cylinder at one end with a passageway connection therefrom intosaid casing; a counter including a plurality of numbers wheels rotatablymounted on a hollow shaft, said counter being disposed in said casingwith said hollow shaft substantially concentric with the longitudinalaxis of said casing and with said numbers wheels exposed therethrough; asecond shaft concentrically passing through said first shaft beyond bothends thereof, a plunger assembly in said passageway including meansnormally urging said plunger assembly toward the proximate end of saidsecond shaft, a disconnectible drive between said second shaft and saidplunger assembly, and means for actuating said counter in accordancewith drive movement of said second shaft.

2. A buret assembly comprising a substantially cylindrical casing havinga liquid cylinder at one end with a passageway connection therefrom intosaid casing; a counter including a plurality of numbers wheels rotatablymounted on a hollow shaft, said counter being disposed in said casingwith said hollow shaft substantially concentric with the longitudinalaxis of said casing and with said numbers wheels exposed therethrough; asecond shaft concentrically passing through said first shaft beyond bothends thereof and having that end facing said liquid cylinder, externallythreaded; a fractional nut; pivot means sliclably supporting saidfractional nut in said casing in position for threadedly engaging thethreaded end of said second shaft; means normally urging said fractionalnut into engagement with said threaded shaft end whereby upon rotationof said second shaft, said fractional nut will be driven along saidpivot means; a plunger assembly in said passageway including meansnormally urging said plunger assembly into engagement with the proximateend of said fractional nut, said plunger assembly being of a length tomove a substantial distance into said cylinder with travel of saidfractional nut on said pivot means in response to rotation of saidsecond shaft; means for manually rotating said second shaft; means drivecoupling said counter to said shaft rotating means to record on saidcounter, movements of said plunger assembly; flange and said firstnumbers wheel; and means for restoring said plunger assembly and saidfractional nut to their initial starting position.

3. A buret assembly comprising a substantially cylindrical casing havinga liquid cylinder at one end with a passageway connection therefrom intosaid casing; a counter including a plurality of numbers wheels rotatablymounted on a hollow shaft, said counter being disposed in said casingwith said hollow shaft substantially concentric with the longitudinalaxis of said casing and with said numbers wheels exposed therethrough; asecond hollow shaft concentrically passing through said first hollowshaft beyond both ends thereof and having that end facing said liquidcylinder, externally threaded; a fractional nut; pivot means slidablysupporting said fractional nut in said casing in position for threadedlyengaging the threaded end of said second hollow shaft; spring meansnormally urging said fractional nut into engagement with said threadedshaft end whereby upon rotation of said second hollow shaft, saidfractional nut will be driven along said pivot means; a plunger assemblyin said passageway including spring means normally urging said plungerassembly into engagement with the proximate end of said fractional nut,said plunger assembly being of a length to move a substantial distanceinto said cylinder with travel of said fractional nut on said pivotmeans in response to rotation of said hollow shaft; means for manuallyrotating said second hollow shaft from its other end; means drivecoupling said counter to said shaft rotating means to record on saidcounter, movements of said plunger assembly; flange and said firstnumbers wheel; means for restoring said p unger assembly and saidfractional nut to their initial starting position, said means includinga push pin passing into said casing through the wall thereof and adaptedunder application of pressure thereto, to lift said fractional nut outof threaded engagement with the threaded end of said second hollowshaft; and means for resetting said counter following restoration ofsaid plunger assembly.

4. A buret assembly comprising a substantially cylindrical casing havinga liquid cylinder at one end with a passageway connection therefrom intosaid casing, and Window openings adjacent its other end; a counterincluding a plurality of numbers wheels rotatably mounted on a hollowshaft, said counter being disposed in said casing with said hollow shaftsubstantially concentric with the longitudinal axis of said casing andwith said numbers wheels exposed through said Window openings; a secondhollow shaft concentrically passing through said first hollow shaftbeyond both ends thereof and having that end facing said liquidcylinder, externally threaded; a fractional nut; pivot means slidablysupporting said fractional nut in said casing in position for threadedlyengaging the threaded end of said second hollow shaft; means normallyurging said fractional nut into engagement with said threaded shaft endwhereby upon rotation of said second hollow shaft, said fractional nutwill be driven along said pivot means; a plunger assembly in saidpassageway including spring means normally urging said plunger assemblyinto engagement with the proximate end of said fractional nut, saidplunger assembly being of a length to move a substantial distance intosaid cylinder with travel of said fractional nut on said pivot means inresponse to rotation of said second hollow shaft; means for manuallyrotating said second hollow shaft; means drive coupling said counter tosaid shaft rotating means to record on said counter, movements of saidplunger assembly; means for restoring said plunger assembly and saidfractional nut to their initial starting position, said means includinga push pin passing into said casing through the wall thereof and adaptedunder application of pressure thereto, to lift said fractional nut outof threaded engagement with the threaded end of said second hollowshaft; and means for resetting said counter following restoration ofsaid plunger assembly.

5. A buret assembly comprising a substantially cylindrical casing havinga liquid cylinder at one end with a passageway connection therefrom intosaid casing; a counter including a plurality of numbers wheels rotatablymounted on ahollow shaft, said counter being disposed in said casingwith said hollow shaft substantially concentric with the longitudinalaxis of said casing and with said numbers wheels exposed therethrough; asecond hollow shaft concentrically passing through said first shaftbeyond both ends thereof, a plunger assembly in said passagewayincluding means normally urging said plunger assembly toward theproximate end of said second shaft, a diseonnectible drive betweensaidshaft and said plunger assembly, means for actuating said counter inaccordance with drive movement of said second shaft, and a push rodextending down through said second hollow shaft into contact with saidplunger assembly.

References Cited in the file of this patent UNITED STATES PATENTS

